A meta-analytic review of the Bethesda System for Reporting Thyroid Cytopathology: Has the rate of malignancy in indeterminate lesions been underestimated?

Deep learning models for thyroid nodules diagnosis of fine-needle aspiration biopsy: a retrospective, prospective, multicentre study in China

BACKGROUND

Accurately distinguishing between malignant and benign thyroid nodules through fine-needle aspiration cytopathology is crucial for appropriate therapeutic intervention. However, cytopathologic diagnosis is time consuming and hindered by the shortage of experienced cytopathologists. Reliable assistive tools could improve cytopathologic diagnosis efficiency and accuracy. We aimed to develop and test an artificial intelligence (AI)-assistive system for thyroid cytopathologic diagnosis according to the Thyroid Bethesda Reporting System.

METHODS

11 254 whole-slide images (WSIs) from 4037 patients were used to train deep learning models. Among the selected WSIs, cell level was manually annotated by cytopathologists according to The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) guidelines of the second edition (2017 version). A retrospective dataset of 5638 WSIs of 2914 patients from four medical centres was used for validation. 469 patients were recruited for the prospective study of the performance of AI models and their 537 thyroid nodule samples were used. Cohorts for training and validation were enrolled between Jan 1, 2016, and Aug 1, 2022, and the prospective dataset was recruited between Aug 1, 2022, and Jan 1, 2023. The performance of our AI models was estimated as the area under the receiver operating characteristic (AUROC), sensitivity, specificity, accuracy, positive predictive value, and negative predictive value. The primary outcomes were the prediction sensitivity and specificity of the model to assist cyto-diagnosis of thyroid nodules.

FINDINGS

The AUROC of TBSRTC III+ (which distinguishes benign from TBSRTC classes III, IV, V, and VI) was 0·930 (95% CI 0·921-0·939) for Sun Yat-sen Memorial Hospital of Sun Yat-sen University (SYSMH) internal validation and 0·944 (0·929 - 0·959), 0·939 (0·924-0·955), 0·971 (0·938-1·000) for The First People's Hospital of Foshan (FPHF), Sichuan Cancer Hospital & Institute (SCHI), and The Third Affiliated Hospital of Guangzhou Medical University (TAHGMU) medical centres, respectively. The AUROC of TBSRTC V+ (which distinguishes benign from TBSRTC classes V and VI) was 0·990 (95% CI 0·986-0·995) for SYSMH internal validation and 0·988 (0·980-0·995), 0·965 (0·953-0·977), and 0·991 (0·972-1·000) for FPHF, SCHI, and TAHGMU medical centres, respectively. For the prospective study at SYSMH, the AUROC of TBSRTC III+ and TBSRTC V+ was 0·977 and 0·981, respectively. With the assistance of AI, the specificity of junior cytopathologists was boosted from 0·887 (95% CI 0·8440-0·922) to 0·993 (0·974-0·999) and the accuracy was improved from 0·877 (0·846-0·904) to 0·948 (0·926-0·965). 186 atypia of undetermined significance samples from 186 patients with BRAF mutation information were collected; 43 of them harbour the BRAFV600E mutation. 91% (39/43) of BRAFV600E-positive atypia of undetermined significance samples were identified as malignant by the AI models.

INTERPRETATION

In this study, we developed an AI-assisted model named the Thyroid Patch-Oriented WSI Ensemble Recognition (ThyroPower) system, which facilitates rapid and robust cyto-diagnosis of thyroid nodules, potentially enhancing the diagnostic capabilities of cytopathologists. Moreover, it serves as a potential solution to mitigate the scarcity of cytopathologists.

FUNDING

Guangdong Science and Technology Department.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Diagnostic values of SurePath liquid-based cytology versus conventional smear in thyroid aspiration samples: A 13-year experience at a single institution

BACKGROUND

Fine needle aspiration cytology (FNAC) is the most useful tool in the diagnosis of thyroid nodules. Liquid-based cytology (LBC) is replacing the conventional smear (CS) for evaluation of thyroid FNAC. In our institution, thyroid FNAC preparation was changed from CS to LBC SurePath in July 2016. This study aimed to compare the diagnostic value of SurePath with that of CS in thyroid lesions.

METHODS

A total of 35,406 samples of thyroid FNAC (11,438 CS and 23,968 SurePath), collected from January 2010 to December 2022, were included in this study. We also examined the malignant rate using the surgical pathology diagnosis as the gold standard.

RESULTS

The distribution of TBSRTC cytological categories was equivalent between CS and SurePath. The rate of nondiagnostic/unsatisfactory category was higher in CS compared to SurePath (43.4% vs. 22.3%; p < .05). After routine use of SurePath, the surgical resection rate was reduced from 12.0% to 8.6% (p < .05) and the malignant rate increased from 32.2% to 41.5% (p < .05). The sensitivities of CS and SurePath were 71.0% and 82.0%, respectively, and the specificities were 99.0% and 97.3%, respectively, whereas the positive predictive values were 97.8% and 96.8%, respectively, and the negative predictive values were 85.0% and 84.6%, respectively. Diagnostic accuracy of CS and SurePath were 88.5% and 89.7% respectively.

CONCLUSION

SurePath can increase the sample adequacy, increase the sensitivity and reduce the workload and avoid unnecessary surgeries with similar accuracy to CS.

Improved Diagnostic Accuracy of Thyroid Fine-Needle Aspiration Cytology with Artificial Intelligence Technology

Background: Artificial intelligence (AI) is increasingly being applied in pathology and cytology, showing promising results. We collected a large dataset of whole slide images (WSIs) of thyroid fine-needle aspiration cytology (FNA), incorporating z-stacking, from institutions across the nation to develop an AI model. Methods: We conducted a multicenter retrospective diagnostic accuracy study using thyroid FNA dataset from the Open AI Dataset Project that consists of digitalized images samples collected from 3 university hospitals and 215 Korean institutions through extensive quality check during the case selection, scanning, labeling, and reviewing process. Multiple z-layer images were captured using three different scanners and image patches were extracted from WSIs and resized after focus fusion and color normalization. We pretested six AI models, determining Inception ResNet v2 as the best model using a subset of dataset, and subsequently tested the final model with total datasets. Additionally, we compared the performance of AI and cytopathologists using randomly selected 1031 image patches and reevaluated the cytopathologists' performance after reference to AI results. Results: A total of 10,332 image patches from 306 thyroid FNAs, comprising 78 malignant (papillary thyroid carcinoma) and 228 benign from 86 institutions were used for the AI training. Inception ResNet v2 achieved highest accuracy of 99.7%, 97.7%, and 94.9% for training, validation, and test dataset, respectively (sensitivity 99.9%, 99.6%, and 100% and specificity 99.6%, 96.4%, and 90.4% for training, validation, and test dataset, respectively). In the comparison between AI and human, AI model showed higher accuracy and specificity than the average expert cytopathologists beyond the two-standard deviation (accuracy 99.71% [95% confidence interval (CI), 99.38-100.00%] vs. 88.91% [95% CI, 86.99-90.83%], sensitivity 99.81% [95% CI, 99.54-100.00%] vs. 87.26% [95% CI, 85.22-89.30%], and specificity 99.61% [95% CI, 99.23-99.99%] vs. 90.58% [95% CI, 88.80-92.36%]). Moreover, after referring to the AI results, the performance of all the experts (accuracy 96%, 95%, and 96%, respectively) and the diagnostic agreement (from 0.64 to 0.84) increased. Conclusions: These results suggest that the application of AI technology to thyroid FNA cytology may improve the diagnostic accuracy as well as intra- and inter-observer variability among pathologists. Further confirmatory research is needed.

Diagnostic models for predicting malignancy in thyroid nodules classified as Bethesda Category III in an endemic region

BACKGROUND

This study aims to develop a diagnostic model to help physicians determine whether thyroid nodules categorized as atypia of undetermined significance (AUS) in category III of the Bethesda system are benign or malignant preoperatively. To create a diagnostic model for predicting thyroid nodules' benign or malignant with AUS cytology based on clinical, ultrasonographic, and cytopathological findings.

METHODS

This is a retrospective cohort study involving patients (>19) at risk of thyroid cancer who had thyroidectomy after an AUS cytology. The dataset consists of 53 variables 204 nodules from 183 patients. Binary logistic regression and factor analysis methods were used to identify risk factors for malignancy. Finally, four prediction models were developed using different approaches, based on clinical, pathological clinical + pathological, and the factors.

RESULTS

A total of 88 (48.1%) of 183 patients diagnosed with AUS were benign and 95 (51.9%) the malignant. After determining risk factors, four prediction models were developed based on different approaches to assist physicians in deciding to detect AUS nodules early. It was seen that bilaterality was found to be a risk factor for malignancy in the clinical model (pbilaterality  = .03) and it was also seen that the pathological variables pale chromatin and irregular contours in the oncocyte variables were risk factors for malignancy (ppalechromatin  = .02, pirregularcontoursintheoncocyte  = .04). The best model obtained sensitivity and specificity values are 73% and 87% based on clinical and pathological variables.

CONCLUSION

This comprehensive study may provide a more in-depth understanding of AUS and make a notable contribution to healthcare professionals before surgery.

The Diagnostic Role of Repeated Biopsy of Thyroid Nodules with Atypia of Undetermined Significance with Architectural Atypia on Core-Needle Biopsy

BACKGRUOUND

We aimed to evaluate the utility of repeat biopsy of thyroid nodules classified as atypia of undetermined significance with architectural atypia (IIIB) on core-needle biopsy (CNB).

METHODS

This retrospective study evaluated patients with thyroid nodules categorized as IIIB on CNB between 2013 and 2015. Demographic characteristics, subsequent biopsy results, and ultrasound (US) images were evaluated. The malignancy rates of nodules according to number of CNBs and the number of IIIB diagnoses was compared. Demographic and US features were evaluated to determine factors predictive of malignancy.

RESULTS

Of 1,003 IIIB nodules on CNB, the final diagnosis was determined for 328 (32.7%) nodules, with 121 of them confirmed as malignant, resulting in a malignancy rate of 36.9% (95% confidence interval, 31.7% to 42.1%). Repeat CNB was performed in 248 nodules (24.7%), with 75 (30.2%), 131 (52.8%), 13 (5.2%), 26 (10.5%), one (0.4%), and two (0.8%) reclassified into categories II, IIIB, IIIA, IV, V, and VI, respectively. Malignancy rates were not significantly affected by the number of CNBs (P=0.291) or the number of IIIB diagnoses (P=0.473). None of the nodules confirmed as category II on repeat CNB was malignant. US features significantly associated with malignancy (P<0.003) included solid composition, irregular margins, microcalcifications, and high suspicion on the US risk stratification system.

CONCLUSION

Repeat biopsy of nodules diagnosed with IIIB on CNB did not increase the detection of malignancy but can potentially reduce unnecessary surgery. Repeat biopsy should be performed selectively, with US features guiding the choice between repeat biopsy and diagnostic surgery.

Two-tier subclassification of the Bethesda category III (atypia of undetermined significance/follicular lesion of undetermined significance) in thyroid cytology

BACKGROUND

The Bethesda category III, AUS/FLUS, comprises a heterogeneous group of thyroid lesions with variable risk of malignancy (ROM). This study evaluates ROM in two subgroups of this category based on nuclear atypia and architectural atypia.

METHODS

Cases in Bethesda category III were reported based on nuclear atypia (AUS) and architectural atypia (FLUS). ROM was calculated by comparing the cytologic diagnosis to the follow-up histologic diagnosis.

RESULTS

Among the 610 Bethesda category III cases in this study, 306 (50.2%) and 304 (49.8%) cases were reported as AUS and FLUS, respectively. One hundred and eighty six of 306 AUS (60.8%) and 193 of 304 FLUS (63.5%) cases underwent surgical intervention. ROM of the cases in Bethesda category III was 12.8% if all cases were counted and 20.6% if only surgical cases were counted. When analyzing separately, ROM of AUS cases was 17.0% and 28.0% with all cases and surgical cases only, respectively. For FLUS cases, ROM was 8.6% and 13.5% with all cases and surgical cases only, respectively.

CONCLUSION

In Bethesda category III, ROM in the cases with nuclear atypia was significantly higher than the cases with architectural atypia. Sub-classifying the Bethesda Category III cases with nuclear atypia and architectural atypia, respectively may better stratify the ROM.

Evaluating local thyroid cytopathology practices by molecular quality metrics: A multi-institutional study on 4651 FNAs with a focus on the role of the interventional cytopathologist

BACKGROUND

The diagnostic accuracy of thyroid fine-needle aspiration (FNA) can be highly influenced by the technical skills of the operator performing the procedure and by interobserver variability in microscopic interpretation. This is particularly true for the indeterminate categories. Recently, molecular testing has been proposed as an ancillary tool for monitoring the performance of different thyroid cytopathology practices. The objective of this multicenter study was to evaluate the quality of different local cytopathology practices by assessing the impact of interventional cytopathologists on FNA adequacy for molecular testing and the variations in mutation rates across different health care centers operating in the Campania region.

METHODS

The study included 4651 thyroid FNA samples diagnosed in different Southern Italian clinical laboratories belonging to the TIRNET (the Tiroide Network). FNA samples were collected by different proceduralists and were classified by local cytopathologists according to The Bethesda System for Reporting Thyroid Cytopathology. FNAs classified as atypia of undetermined significance, follicular neoplasm, suspicious for malignancy, and malignant were centralized for a real-time polymerase chain reaction-based, seven-gene test at the authors' institution.

RESULTS

Centers that employed interventional cytopathologists obtained fewer unsatisfactory FNA samples for molecular testing (11.3%) than centers that employed noncytopathologists (16.7%; p < .05). Furthermore, a significant variation in the mutation rate was observed in FNAs diagnosed by different local cytopathologists; indeterminate categories had the highest percentage of mutation rate variability among centers.

CONCLUSIONS

Interventional cytopathologists obtained higher yields of diagnostic material for molecular testing. Finally, the current results suggest that the variability in mutation rates among different centers may highlight the low reproducibility of microscopic criteria among cytopathologists, particularly for indeterminate cases.

Performance of ACR TI-RADS and the Bethesda System in Predicting Risk of Malignancy in Thyroid Nodules at a Large Children's Hospital and a Comprehensive Review of the Pediatric Literature

While thyroid nodules are less common in children than in adults, they are more frequently malignant. However, pediatric data are scarce regarding the performance characteristics of imaging and cytopathology classification systems validated to predict the risk of malignancy (ROM) in adults and select those patients who require fine-needle aspiration (FNA) and possibly surgical resection. We retrospectively reviewed the electronic medical records of all patients 18 years of age or younger who underwent thyroid FNA at our institution from 1 July 2015 to 31 May 2022. Based on surgical follow-up from 74 of the 208 FNA cases, we determined the ROM for the American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) ultrasound risk stratification system and The Bethesda System for Reporting Thyroid Cytopathology and added our results to those of pediatric cohorts from other institutions already published in the literature. We found the following ROMs for 1458 cases using ACR TI-RADS (TR): TR1. Benign: 2.2%, TR2. Not Suspicious: 9.3%, TR3. Mildly Suspicious: 16.6%, TR4. Moderately Suspicious: 27.0%, and TR5. Highly Suspicious 76.5%; and for 5911 cases using the Bethesda system: Bethesda I. Unsatisfactory: 16.8%, Bethesda II. Benign: 7.2%, Bethesda III: Atypia of Undetermined Significance: 29.6%, Bethesda IV. Follicular Neoplasm: 42.3%, Bethesda V. Suspicious for Malignancy: 90.8%, and Bethesda VI. Malignant: 98.8%. We conclude that ACR TI-RADS levels imply higher ROMs for the pediatric population than the corresponding suggested ROMs for adults, and, in order to avoid missing malignancies, we should consider modifying or altogether abandoning size cutoffs for recommending FNA in children and adolescents whose thyroid glands are smaller than those of adults. The Bethesda categories also imply higher ROMs for pediatric patients compared to adults.

The national rate of malignancy among Bethesda III, IV, and V thyroid nodules is higher than expected: A NSQIP analysis

BACKGROUND

The Bethesda System for Reporting Thyroid Cytopathology was formalized in 2007 to stratify cytologic specimens based on their risk of malignancy. Several studies have reported significant variations between their institutional rate of malignancy compared to the Bethesda System for Reporting Thyroid Cytopathology. The objective of this study was to determine the national rate of malignancy for Bethesda III, Bethesda IV, and Bethesda V thyroid nodules.

METHODS

From 2016 to 2019, patients with preoperative thyroid cytopathology and pathology results in National Surgical Quality Improvement database were included. The rate of malignancy was compared to the median the Bethesda System for Reporting Thyroid Cytopathology 2017, and risk factors associated with malignancy were identified for Bethesda III, Bethesda IV, and Bethesda V specimens.

RESULTS

In total, 13,121 patients with preoperative cytopathology and postresection pathology were identified. The national rate of malignancy was significantly higher than the Bethesda System for Reporting Thyroid Cytopathology 2017 for Bethesda III (36.2% vs 12.0%, P < .01), Bethesda IV (36.7% vs 25.0%, P < .01), and Bethesda V (91.1% vs 52.5%, P < .01) specimens. Male sex was significantly associated with malignancy in Bethesda III, Bethesda IV, and Bethesda V nodules (Bethesda III, odds ratio: 1.20, [1.01-1.42]; Bethesda IV, odds ratio: 1.47, [1.27-1.71]; Bethesda V, odds ratio: 1.28, [1.03-1.58]). Younger age was associated with malignancy in Bethesda III patients under 55 (odds ratio: 1.23, [1.06-1.42]), Bethesda IV patients under 42 (odds ratio: 1.23, [1.06-1.43]), and Bethesda V patients aged less than 47 (odds ratio: 1.38, [1.15-1.67]).

CONCLUSIONS

This is the largest cohort study to describe the national rate of malignancy for Bethesda III, IV, and V specimens in the United States. These results reveal the national rate of malignancy is higher than the implied rate of malignancy reported to patients based on the Bethesda System for Reporting Thyroid Cytopathology. We recommend counseling patients regarding this increased rate of malignancy to set appropriate expectations after surgical intervention.

The clinical significance of the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) category 5 thyroid nodules: Not as risky as we think?

BACKGROUND

Although the prevalence of thyroid nodules is high, few prove to be malignant. Based on sonographic features, the American College of Radiology Thyroid Imaging Reporting and Data System categorizes malignancy risk of thyroid nodules with associated management recommendations for each category level. Malignancy rates among nodules with a highly suspicious Thyroid Imaging Reporting and Data System category 5 warrant examination in the context of additional risk stratification tools, including cytopathology and molecular testing.

METHODS

All patients who underwent fine-needle aspiration biopsy for Thyroid Imaging Reporting and Data System category 5 nodules from January 2018 to September 2021 in a large integrated academic health system were reviewed. Using the Bethesda System for Reporting Thyroid Cytopathology, categories V and VI were set as malignant. Molecular testing (ThyroSeq version 3; Rye Brook, NY) yielding ≥50% risk of malignancy was deemed positive and correlated with surgical pathology.

RESULTS

A total of 496 Thyroid Imaging Reporting and Data System category 5 nodules were identified. On fine-needle aspiration cytopathology, 61 (12.3%) were malignant. The breakdown included Bethesda System for Reporting Thyroid Cytopathology I, 15 (3%); II, 362 (73%); III, 52 (10.5%); IV, 5 (1%); V, 6 (1.3%); and VI, 55 (11.1%). Of Bethesda System for Reporting Thyroid Cytopathology III/IV nodules with molecular testing (n = 53), 24.5% yielded positive results. In total, 42 (8.5%) nodules underwent surgical resection, most of which were Bethesda System for Reporting Thyroid Cytopathology VI (n = 26, 61.9%). Of excised nodules, 33 (78.6%) nodules were malignant, 6 (14.3%) benign, and 3 (7.1%) noninvasive follicular thyroid neoplasm with papillary-like nuclear features. All Thyroid Imaging Reporting and Data System category 5 nodules with malignant cytology (Bethesda System for Reporting Thyroid Cytopathology V/VI) that underwent surgery were malignant on histopathology. On average, the total Thyroid Imaging Reporting and Data System points were higher in malignant nodules compared with benign (9.3 vs 7.3; P = .015). Moreover, benign nodules more frequently received Thyroid Imaging Reporting and Data System points when the radiologist was unable to determine composition or echogenicity (33% vs 3% among malignant nodules; P = .01).

CONCLUSION

Thyroid Imaging Reporting and Data System category 5 designation in thyroid nodules is associated with a lower risk of malignancy than previously reported. Benign and malignant nodules with Thyroid Imaging Reporting and Data System category 5 designation have discrepancies in certain Thyroid Imaging Reporting and Data System characteristics and individual points assigned, which may offer an opportunity for quality improvement and standardization measures in ultrasound reporting practices.

Thyroid Nodules with Indeterminate FNAC According to the Italian Classification System: Prevalence, Rate of Operation, and Impact on Risk of Malignancy. An Updated Systematic Review and Meta-analysis

A thyroid nodule classified as indeterminate on fine-needle aspiration cytology (FNAC), hereafter referred to as an indeterminate thyroid nodule (ITN), represents a clinical dilemma. The Italian Consensus for the Classification and Reporting of Thyroid Cytology (ICCRTC) divides ITNs into low- and high-risk categories (i.e., TIR3A and TIR3B, respectively) to better manage patients. This study aimed to achieve high-evidence estimates of the prevalence, rate of operation, and risk of malignancy of ITNs, including TIR3A and TIR3B ITNs. This systematic review was conducted according to MOOSE to retrieve all original studies citing ICCRTC. The last search was performed in February 2022. The risk of bias of the included studies was assessed. Separate proportion meta-analyses were performed with a random-effect model using OpenMeta[Analyst]. The online search processed 271 studies, and 33 were finally considered. First, the cancer prevalence among ITNs was 32.4%. Second, the cancer prevalence among TIR3As was 12.4%, with heterogeneity (I₂ 90%) explained by a linear correlation between sample size and cancer rate (p = 0.009). Third, the cancer prevalence among TIR3Bs was 44.4%, with heterogeneity (I₂ 75%) explained by the inverse correlation between sample size and cancer rate (p = 0.031). Fourth, the prevalence of ITNs, TIR3A, and TIR3B among FNACs was 29.6%, 12.6%, and 12.9%, respectively, with sample size and TIR3B prevalence being inversely correlated (p = 0.04). Fifth, the operation rates of ITNs, TIR3A, and TIR3B were 54.3%, 48.3%, and 75.2%, respectively, and the sample size and TIR3A operation rate were inversely correlated (p = 0.010). These data strongly support the division of ITNs into low- and high-risk subcategories. Importantly for clinical practice, the cancer rate among ITNs is significantly influenced by the study sample size.

Comparison between total thyroidectomy and hemithyroidectomy in TIR3B thyroid nodules management

PURPOSE

Thyroid nodules classified as TIR3B according to SIAPEC 2014 are considered a clinical challenge due to the risk to be malignant. This retrospective study aimed to compare the performances of total thyroidectomy (TT) and hemithyroidectomy (HT) in the surgical management of a consecutive cohort of patients affected by TIR3B thyroid nodule in terms of side effects and the rate of malignancy detected.

METHODS

From 2011 to 2019, 136 (111 women, 25 men; average age of 53.5 years) patients having a thyroid nodule with a cytological diagnosis of TIR3B who underwent TT or HT were retrospectively included.

RESULTS

Out of 136 patients, 106 (78%) received TT, while the remaining 30 (22%) HT. The final diagnosis was malignant in 65 patients (48%), with follicular variant of papillary carcinoma as the most frequent. The diagnosis of malignancy was significantly more common in the TT group with 56 patients (53%) compared to the HT group with 9 cases (30%) (p = 0.001). Patients who underwent TT were significantly older, had larger nodules and the time between diagnosis and surgery was significantly longer compared to HT (p = 0.001; p0.003; p = 0.002). No main post-surgical complications were registered, except for one case of transient hypocalcemia in a patient who underwent TT.

CONCLUSIONS

Our data showed a malignancy rate of TIR3B lesions higher than expected (48%). Both TT and HT seem to be effective approaches for the treatment of TIR3B nodules with a very low rate of post-surgical comorbidities. In the choice of surgical approach, it is crucial to consider the presence of risk factors (clinical and ultrasound characteristics), nodule size, patients' opinion, and surgeon's skills and experience.

Association of patient characteristics, ultrasound features, and molecular testing with malignancy risk in Bethesda III–V thyroid nodules

Objective

To evaluate the role of patient characteristics, ultrasound findings, and molecular testing in predicting risk of malignancy in Bethesda III, IV, and V thyroid nodules.

Design

Single institution retrospective review of 230 patients with Bethesda III, IV, and V cytopathology undergoing thyroidectomy between 2009 and 2018.

Setting

Private and public tertiary urban university hospitals at the same academic institution.

Subjects and methods

Patients who underwent thyroidectomy with Bethesda III, IV, and V nodules were included. Patient demographics, presence of underlying thyroid disease, nodule size, sonographic features, gene expression results, and surgical procedure were documented. Correlation between these variables and final histopathologic diagnosis of malignancy was analyzed.

Results

The 230 patients (103 Bethesda III, 64 Bethesda IV, and 63 Bethesda V) were included for analysis. Bethesda III nodules harbored malignancy in 26.2% of cases compared with 26.6% of Bethesda IV nodules and 82.5% of Bethesda V nodules. On multivariate analysis, age was inversely correlated with a diagnosis of malignancy (OR: 0.98, 95% confidence interval [CI]: 0.96–0.99, p = .03) Although the presence of microcalcifications was positively associated with cancer (OR: 2.31, CI: 1.24–4.29, p = .008) The co‐occurrence of microcalcifications and irregular margins was associated with a higher odds of malignancy (OR: 4.42, 95% CI: 1.32–14.93, p = .016), whereas the combination of microcalcifications, irregular margins, and hypoechogenicity was associated with the greatest cancer risk (OR: 5.52, 95% CI: 1.12–27.78, p = .036).

Conclusions

The presence of microcalcifications in thyroid nodules categorized as Bethesda III–V is an independent risk factor for malignancy. The combination of microcalcifications, irregular margins, and hypoechogenicity is associated with a greater malignancy risk in nodules indeterminate for thyroid cancer on cytopathology.

Thyroid nodules of indeterminate cytology in Hispanic/Latinx patients

BACKGROUND

Behavior of differentiated thyroid cancer (DTC) varies among ethnic groups. Recommended management of thyroid nodules with indeterminate cytology (TN-IC) is based on molecular analysis from predominantly non-Hispanic white patients. We hypothesized that TN-IC in Hispanic/Latinx patients would have different features, management, and outcomes and that molecular testing might perform differently in Hispanic/Latinx patients.

METHODS

Retrospective chart review was performed on 127 TN-IC analyzed with Afirma. Patient characteristics were compared using linear model ANOVA and Fisher's exact test.

RESULTS

Out of 127 TN-IC, 71 (56%) were Hispanic/Latinx. Hispanic/Latinx had a greater prevalence of diabetes, but Afirma results (benign or suspicious) were similar between ethnic groups. Fourteen patients had malignant pathology. Their management and outcomes were similar across groups. The negative predictive value for our cohort (97.9%) was similar to published data.

CONCLUSIONS

Data from our predominantly-Hispanic/Latinx cohort suggest that Afirma performs similarly in Hispanic/Latinx and non-Hispanic white patients with TN-IC.

Outcomes of the Bethesda system for reporting thyroid cytopathology in community- vs. institution-performed cytology

OBJECTIVES

Despite the important role of the community in the assessment and risk stratification of patients with thyroid nodules, evidence-based data on the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) performance in community clinics is lacking. We aim to evaluate BSRTC performance of aspirations taken in community clinics compared with primary referral center.

METHODS

Patients who underwent thyroid surgery between 2013 and 2018 at our institution were divided according to the fine needle aspirations (FNA) settings: community FNA (cFNA) vs. institutional FNA (iFNA). Demographics, BSRTC results and final pathology were collected. Diagnostic values were calculated for BSRTC categories (sensitivity, specificity, positive predictive value [PPV], and negative predictive value [NPV]), and were compared between the groups.

RESULTS

A total of 268 nodules were included in the study; 77% (207) cFNA and 23% (61) iFNA. Patients in the community were younger (51.7 ± 15.1 vs. 56.6 years±14.8, p = 0.03) and with less epidemiology risk factors for thyroid cancer (1.9% vs 13.1%, p < 0.001). cFNA malignancy rate for BSRTC I-VI was 0%, 6.4%, 11.8%, 32.1%, 91.6% and 93.8% respectively. Best sensitivity was found for BSRTC III-VI in both groups (88% and 83%, cFNAs and iFNAs, respectively). Overall best performance was obtained for BSRTC V-VI for both groups (cfNA: 85%, 97%, 93%, 94% and 93%; iFNAs: 81%, 100%, 100%, 87% and 91%, for sensitivity, specificity, PPV, NPV and accuracy, respectively).

CONCLUSIONS

Community-performed FNAs demonstrate acceptable BSRTC distribution and malignancy rates, comparable with a primary referral academic hospital. This supports the universality of the BSRTC 2017 and its recommendations also in the community.

Predictive Value of a Genomic Classifier in Indeterminate Thyroid Nodules Based on Nodule Size

Importance

Genomic classifiers were developed to better guide clinicians in the treatment of indeterminate thyroid nodules (ITNs). To our knowledge, whether there is variation in the diagnostic accuracy of these tests depending on ITN size has not been previously studied.

Objective

To analyze the diagnostic performance of a genomic classifier in relation to ITN size.

Design, Setting, and Participants

A case series study with medical records review was conducted including all patients with a cytologic diagnosis of ITN managed with genomic classifier testing and surgery from January 2015 to December 2018 at NYU Langone Health. Demographics, ITN characteristics, genomic profiles, treatment, and final pathologic findings were recorded. Data analysis was conducted from March to April 2021.

Main Outcomes and Measures

The primary aim was to assess the positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity of a genomic classifier test (ThyroSeq) in relation to ITN size (<2, 2-4, and >4 cm). The secondary aim was to investigate the risk of cancer associated with genetic signatures.

Results

Of the 212 patients with 218 ITNs, 158 (74.5%) were women; median (SD) age was 49 (15.6) years. Genomic classifier results were positive in 173 ITNs (79.4%) treated with surgery. In this group of 173 positive ITNs, 46 (26.6%) were malignant on final pathologic testing. Overall, the observed cancer prevalence in the population was 23.9% (52 ITNs). In 45 ITNs that underwent surgery despite a negative genomic classifier interpretation, 6 (13.3%) were malignant. The PPV of a positive test was 27% and the NPV was 87%. The PPV and NPV findings improved as the ITN size increased (<2 cm [n = 98]: PPV, 25%; NPV, 79% vs >4 cm [n = 33]: PPV, 50%; NPV, 89%). Test specificity was higher in larger ITNs (<2 cm: 15% vs >4 cm: 40%; P = .01). Isolated RAS sequence variations were the most common variant identified in malignant nodules (11 [21.1%] of all ITNs), followed by BRAF variants (7 [13.5%] of all ITNs).

Conclusions and Relevance

In this case series, the performance of the ThyroSeq test improved for larger ITNs. The risk of cancer in large ITNs with negative test results was low. These data suggest that, in genomic classifier-negative ITNs larger than 4 cm, initial management of thyroid lobectomy may be sufficient.

Rate of malignancy for thyroid nodules with AUS/FLUS cytopathology in a tertiary care center - a retrospective cohort study

BACKGROUND

Thyroid nodules are stratified through fine-needle aspiration (FNA) and are often categorized using The Bethesda System for Reporting Thyroid Cytopathology, which estimates the risk of malignancy for six cytopathological categories. The atypia of undetermined significance (AUS) and follicular lesion of undetermined significance (FLUS) categories have varying malignancy rates reported in the literature which can range from 6 to 72.9%. Due to this heterogeneity, we assessed the malignancy rate and effectiveness of repeat FNA (rFNA) for AUS/FLUS thyroid cytopathology at our institution.

METHODS

Electronic health records of patients with AUS/FLUS thyroid cytopathology on FNA at our center since the implementation of the Bethesda System on May 1, 2014-December 31, 2019 were retrospectively reviewed. Patient demographics, treatment pathway, and pathology results were collected. The treatment pathway of the nodules, the rFNA results, and the malignant histopathology results were reported. Malignancy rates were calculated as an upper and lower limit estimate.

RESULTS

This study described 182 AUS/FLUS thyroid nodules from 177 patients. In total, 24 thyroid nodules were deemed malignant upon histopathology, yielding a final malignancy rate of 13.2-25.3%. All of the malignancies were variants of papillary thyroid carcinoma. The malignancy rate of the nodules which underwent resection without rFNA (21.5%) was lower than the malignancy rate of the nodules which underwent resection after rFNA (43.8%). 45.5% of the rFNA results were re-classified into more definitive categories.

CONCLUSION

The malignancy rate of AUS/FLUS thyroid cytopathology at our center is in line with the risk of malignancy stated by the 2017 Bethesda System. However, our malignancy rate is lower than some other Canadian centers and approximately half of our rFNAs were re-classified, highlighting the importance of establishing center-specific malignancy and rFNA re-classification rates to guide treatment decisions.

Reporting Thyroid Cytology in a Globalized World

The Italian SIAPEC-AIT 2014 classification, the 2017 Bethesda System for Reporting Thyroid Cytology (TBSRTC), the 2016 UK Royal College of Pathologists (RCPath) thyroid reporting system, and the 2019 Japanese reporting system for thyroid aspiration cytology (JRSTAC2019) represent the most widely used reporting systems among clinicians and pathologists for the purpose of cytologically diagnosing, estimating the potential risk of malignancy (ROM), and defining the most appropriate treatment for a patient with a thyroid nodule. Although all the systems use overlapping diagnostic categories and morphologic criteria, they differ on the basis of the criteria for inclusion in the cytologic categories, which may, in turn, affect the ROM of a given category and the clinical management of the patient, particularly with regard to the “indeterminate” categories. The aim of this review is to analyze the main differences that emerge between the systems and to propose possible solutions for a comprehensive reporting system that integrates and harmonizes all the criteria of the Italian classification and the Bethesda system, also taking into account the impact that the new tumor entity NIFTP (non-invasive follicular tumor with papillary-like nuclear features) that has, in many instances, replaced the non-invasive form of the follicular variant of papillary carcinoma, has had on the modification of malignancy risks.

The Use of the Bethesda System for Reporting Thyroid Cytopathology in Pediatric Thyroid Nodules: A Meta-Analysis

Background: Little is known about the application of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) in pediatric thyroid nodules. This meta-analysis was aimed to investigate the use of TBSRTC in the pediatric population. Methods: Relevant articles were searched in PubMed and Web of Science. Meta-analysis of proportion and its 95% confidence interval (CI) were computed utilizing the random-effect model. We used subgroup analyses and meta-regression to explore the sources of heterogeneities. Egger's regression test and funnel plot visualization were used to examine publication bias. Results: We included 17 articles comprising of 3687 pediatric thyroid nodules for meta-analyses. TBSRTC outputs including frequency and risk of malignancy (ROM) for the majority of categories were not statistically different from recently published meta-analysis of 145,066 thyroid nodules in adult patients. The resection rate (RR) in the pediatric group was significantly higher in most of the categories compared with published adult data: benign, 23.2% [CI = 18.6-27.9] vs. 13.0% [CI = 9.5-16.5]; atypia of undetermined significance/follicular lesion of undetermined significance, 62.6% [CI = 50.3-74.9] vs. 36.2% [CI = 29.9-42.5]; follicular neoplasm/suspicious for follicular neoplasm, 84.3% [CI = 75.2-93.4] vs. 60.5% [CI = 54.5-66.5]; and suspicious for malignancy, 93.8% [CI = 90.1-97.6] vs. 69.7% [CI = 64.0-75.5]. Conclusion: TBSRTC is a valuable tool to make clinical decisions for pediatric patients with thyroid nodules. Pediatric patients with benign and indeterminate thyroid nodules had a higher RR than adult counterpart, but ROM of these categories in adults and children was not statistically different suggesting a potential risk of overtreatment in pediatric patients. Determining the best treatment guidelines and additional tools for risk stratification must be a top priority to precisely identify the target patient groups for surgical intervention.

Malignancy outcomes and the impact of repeat fine needle aspiration of thyroid nodules with Bethesda category III cytology: A multicenter experience

BACKGROUND

The clinical management of Bethesda III category thyroid nodules has some undefined points and differs among centers and conflicting malignancy rates are present in the literature. The aim of this study was to investigate the Bethesda category III thyroid nodule outcomes in our centers, to determine malignancy rates and also to evaluate clinical and sonographic features which may help to predict malignancy.

METHODS

This retrospective study included 333 patients with thyroid nodules who had Bethesda category III on fine needle aspiration (FNA) in three tertiary medical centers of Turkey.

RESULTS

Among 333 patients, 302 had appropriate follow up. Eighteen patients received thyroidectomy after the first FNA, with a malignancy rate of 38.89% (7/18) and 284 patients received a second FNA. After the second FNA, thyroidectomy was performed in 80 patients and 41 patients needed the third FNA. Thirteen thyroidectomies were performed after the third FNA. Totally 111 patients received thyroidectomy with a malignancy rate of 48.65% (54/111) among patients with surgery and the lower bound was detected as 17.88% (54/302). Of these patients the malignancy rates of patients receiving thyroidectomy with two and three FNAs were 47.50% (38/80) and 69.23% (9/13), respectively. Hypoechogenicity, microcalcification, and irregular margin were found as good predictors for malignancy.

CONCLUSION

We demonstrated that the malignancy rate was 48.65% in patients receiving thyroidectomy. We showed a higher malignancy rate than the traditionally rate of 5%-15%. This study showed that repeat FNAs decrease the rate of unnecessary surgery performed for benign lesions by increasing the rate of malignancy detection.

Combining the American Thyroid Association's Ultrasound Classification with Cytological Subcategorization Improves the Assessment of Malignancy Risk in Indeterminate Thyroid Nodules

Background: The risk of malignancy (RoM) of indeterminate thyroid nodules (ITNs) shows a high variability in interinstitutional cohorts. The RoM is partially associated with the cytological degree of atypia and the ultrasound (US) pattern. This study evaluated the cancer risk of ITNs by jointly considering the cytological subcategory and the American Thyroid Association (ATA)-based US risk classification. Methods: This study features a retrospective cohort from two Brazilian centers comprising 238 ITNs with confirmed outcomes. US classification, according to ATA-based guidelines, and cytological subcategorization were determined. The cytological subgroups were as follows: (1) nuclear atypia (NA) related to papillary thyroid carcinoma (PTC) but insufficient to categorize the cytology as suspicious for malignancy; (2) architectural atypia without NA (AA); (3) both architectural and nuclear atypia (ANA); (4) oncocytic pattern (OP) without NA; and (5) NA not related to PTC (NANP). NA was divided into three subgroups: nuclear size and shape, nuclear membrane appearance, and/or chromatin aspects. Results: The overall frequency of malignancy was 39.5%. Among the cytological subcategories, the highest RoM was related to the NA (43.9%) and to the ANA (43.5%), followed by AA (29.4%), and OP (9.4%). NA was positively and independently associated with cancer (odds ratio [OR]: 4.5; confidence interval [CI: 1.2-16.6]) as was the occurrence of ANA (OR 6.6 [CI 1.5-29.5]). AA and OP were not independently associated with cancer. Both ATA-based high- and intermediate-risk categories showed an independent association with cancer (OR 6.8 [CI 2.9-15.5] and OR: 2.6 [CI 1.1-5.8], respectively). ITNs with cytological findings of NA or ANA when combined with intermediate US patterns had RoM values of 47.5% and 56.7%, respectively. Both cytological subcategories, when combined with the ATA high-suspicion class reached an RoM >70%. The type of NA with the highest odds for cancer was related to the nuclear membrane (OR 11.5). Conclusions: The RoM of ITNs can reach almost 80% when both NA and ATA-based high-risk US features are present. The presence of such cytological features also increased the RoM in the ATA-based intermediate-risk US category. In addition, AA and OP were not independently related to higher cancer risk. These results strengthen the recommendations for combing cytological subcategorization and US risk classification in the workup for ITNs before the decision of a molecular testing, clinical observation, or diagnostic surgery.

Thyroid FNA terminology: The case for a single unified international system for thyroid FNA reporting

The use of reporting terminologies for thyroid FNA cytology enables standardisation and international alignment of the reporting of thyroid cytology results, which is essential. There are currently three major internationally recognised systems: Bethesda (TBS), UK RCPath (Thy), and Italian (TIR). A fourth terminology system used in Japan has identical categories to TBS but with different nomenclature. The aim of this review is to discuss the strengths and weaknesses of the TBS, UK RCPath, and TIR systems, and to make the case for international terminology harmonisation and standardisation.

Validating the 'CUT score' risk stratification tool for indeterminate thyroid nodules using the Bethesda system for reporting thyroid cytopathology

PURPOSE

Managing intermediate thyroid nodules remains challenging. The CUT score is an Italian metanalysis-based cytologic (SIAPEC-IAP) scoring system, designed to assist clinicians. However, it was never evaluated against the Bethesda system for reporting thyroid cytopathology (BSRTC). This study aims to validate its utility for BSRTC III and IV nodules in a non-Italian population.

METHODS

We collected all BSRTC III and IV thyroid nodules with a documented final pathology between 2010 and 2020. We calculated the C + U components of the CUT score using retrospective clinical (C) data collection and reevaluation of preoperative sonography (U) examination. The cytology (T) component which originally referred to the five-tiered SIAPEC-IAP cytologic classification was replaced by the corresponding BSRTC categories. Optimal test performances were calculated using receiver operating characteristic (ROC) curve analysis. Data were analyzed twice with considering of NIFTP as benign and as malignant.

RESULTS

After exclusions, 62 nodules from 61 patients were included (50% BSRTC III, 50% BSRTC IV). Malignant nodules demonstrated a significantly higher C + U score compared with benign in both categories. The C + U cutoff value for BSRTC III was 5.25 (sensitivity and specificity of 69.23% and 66.67%, respectively, AUC = 0.72, p-value = 0.016), and 5.75 for BSRTC IV (sensitivity and specificity of 85.7% and 76.5%, respectively, AUC = 0.84, p-value < 0.001).

CONCLUSION

Our study suggests that the CUT score is applicable for both BSRTC III and IV nodules, and highlights the need for internal validations, since the cutoffs found were higher than previously reported.

The Correlation of Age with Prognosis of Atypia of Undetermined Significance and Follicular Lesion of Undetermined Significance in Thyroid Nodules

Purpose

Although some prognostic variables and risk factors for thyroid cancer (TC) are age-related, the association between age and the risk of TC in patients with thyroid nodules (TNs) assigned to atypia of undetermined significance (AUS) and follicular lesion of undetermined significance (FLUS) is poorly estimated. The aim of this study was to assess the histopathology of AUS/FLUS and the risk of TC according to the age of the patients at the time of AUS/FLUS diagnosis.

Patients and Methods

Among 5021 individuals treated for TNs at one institution from 2008 to 2018, 161 (3.2%) patients with 161 TNs assigned to the AUS/FLUS category (1 nodule per patient) were selected and stratified by age at initial diagnosis: <55 years, 55–75 years and >75 years. Logistic regression analysis was used to estimate the association of age with the risk of TC diagnosis.

Results

Ninety-one (56.52%) patients <55 years old, 58 (36.02%) patients 55–75 years old, and 12 (7.45%) individuals >75 years old were identified. There were 130 (80.7%) females and 31 (19.3%) males with a mean age of 50.6 ± 16.12 years. Among the evaluated TNs, 142 (88.2%) were ultimately diagnosed as benign, and 19 (11.8%) were diagnosed as malignant. Younger age in patients was significantly related to malignancy outcome (p=0.024 for age <55 years). Patients aged 55–75 years had a significantly lower risk of TC than the other age categories (p=0.040). The risks of high vascularity and fast tumor growth were significantly higher in the youngest category than in the other categories (age <55 years old: p=0.045 and p=0.002, respectively).

Conclusion

Although patients with TNs classified as AUS/FLUS by ultrasound-guided fine needle aspiration biopsy (UG-FNAB) are not typically qualified for surgery, it is worth noting that younger patients with an AUS/FLUS diagnosis might be at a higher risk of TC.

National differences in cost analysis of Afirma Genomic sequencing classifier

CONTEXT

Thyroid nodules of indeterminate cytology can be subjected to molecular testing such as the Afirma Genomic Sequencing Classifier (GSC), thereby minimizing the number of unnecessary diagnostic surgeries.

OBJECTIVE

This work aimed to evaluate and compare the cost of routine GSC testing of indeterminate thyroid nodules in different countries.

DESIGN, PATIENTS AND MAIN OUTCOME MEASURES

The cost of diagnostic hemithyroidectomy of indeterminate thyroid nodules was calculated by performing a Monte Carlo simulation cost analysis on a Markov decision-analytic model and then compared to that of GSC testing in the UK, Australia, USA, and Israel.

RESULTS

Assuming that patients are treated by surgical resection and routine GSC testing is performed for all nodules of indeterminate significance, we found the GSC test to be more cost effective compared with diagnostic hemithyroidectomy when malignancy rates of thyroid nodules are less than 22.6%-37.1%, depending on the country where the test is performed. Given the cost of a thyroidectomy in the UK, Australia and Israel, performing routine GSC tests on all Bethesda IV nodules is more expensive than routine diagnostic hemithyroidectomy and becomes cost effective for Bethesda III when the GSC cost is below 3,031-3,087 USD. In comparison, in the USA, higher cost of thyroidectomy makes the GSC test cost effective for Bethesda III nodules at its current cost, but not for Bethesda IV nodules where it becomes cost effective under the price of 3,031 USD.

CONCLUSIONS

Different molecular testing and surgical costs in different countries should be considered when performing cost analysis. In addition, since different medical centres have different malignancy rates, personalized in-house assessment of cost-effectiveness is warranted.

The Role of Cell Blocks and Immunohistochemistry in Thyroid Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance Bethesda Category

INTRODUCTION

Thyroid cytology is a widely accepted tool in the clinical triaging of nodular lesions. Cell blocks (CBs) can help in the diagnosis of atypical lesions, namely, thyroid Bethesda category of Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS).

METHODS

In a series of 224 AUS/FLUS thyroid samples with CB, we studied CB cellularity and feasibility of 3 immunohistochemical markers (cytokeratin 19 [CK19], HBME-1, and galectin-3) apart and in combination.

RESULTS

The CBs were non-diagnostic in 34 cases. Twenty-four CBs contained <10 cells, 45 CBs 10-50 cells, and 121 CBs >50 cells. Notably, more cellularity was found in CBs performed by plasma-thrombin and in-house techniques (p < 0.001). The diagnostic accuracy to detect malignancy was 65.1% for CK19, 72.1% for HBME-1, and 70.3% for galectin-3.

CONCLUSION

In conclusion, CB cellularity is essential for successful immunohistochemistry application and further diagnostic workup of AUS/FLUS cases.

Thyroid and Molecular Testing. Advances in Thyroid Molecular Cytopathology

Thyroid nodules are a common finding in the adult population including the fact that more than 50% of individuals, over the age of 60, have thyroid nodules. The majority have been mostly detected with ultrasonography and 10% by palpation. The majority of these nodules are benign, whereas 5–15% of them are malignant. The pre-operative diagnosis of cancer is a critical challenge in order to ensure that each patient can be treated with the best tailored management with a reduction of unnecessary surgery for benign lesions. Fine needle aspiration cytology (FNAC) represents the first and most important diagnostic tool for the evaluation of thyroid lesions. According to the literature, FNAC is able to render a conclusive diagnosis in up to 70–80% of all cases. For the remaining 20–30% of nodules, cytological diagnoses fall into the category of indeterminate lesions mostly due to the lack of specific morphological features. According to the Bethesda system for reporting thyroid cytopathology (TBSRTC), indeterminate lesions can be sub-stratified into three different subcategories including “atypia of undetermined significance/follicular lesion of undetermined significance-AUS/FLUS”; “follicular or Hürthle cell neoplasm/suspicious for follicular or Hürthle cell neoplasm-FN/SFN”; and “suspicious for malignancy-SFM”. Many of these indeterminate lesions undergo repetition or diagnostic lobectomy. Nonetheless, the majority of these cases will have a benign diagnosis due to the fact that the rate of cancer ranges between 6 and 30%. It stands to reason that the application of ancillary technique, mostly molecular testing, emerged as a critical additional tool for those thyroid indeterminate lesions. Since the early 1990s, material collected from cytological samples yields sufficient and adequate cells for the detection of point mutation or gene fusions. Nonetheless, the further availability of new sequencing technologies such as next-generation sequencing (NGS) has led to more comprehensive molecular applications adopted now in clinical use. The current review investigates the multiple advances in the field of molecular testing applied in thyroid cytology.

Revised Bethesda System for Reporting Thyroid Cytology: Lessons learned from an appraisal of 5 years of experience in a central hospital

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytology (BSFRTC) is widely adopted in the management of thyroid nodules. The system was updated in 2017, and its impact is the subject of this paper.

METHODS

All thyroid fine needle aspirations from 2016-2020 using the BSFRTC, with follow-up surgical pathology, were reviewed. The risk of neoplasia (RON), risk of malignancy (ROM), RON/ROM ratio, and surgical follow-up rate were determined for each diagnostic category with cytohistological correlation. ROM was calculated in two separate manners, with non-invasive follicular tumours with papillary-like nuclear features (NIFTP) counted as malignant or non-malignant. Sensitivity, specificity, negative and positive predictive values were determined for indeterminate categories: atypia of undetermined significance (AUS), suspicious for follicular neoplasm (SFN), and suspicious for malignancy (SFM).

RESULTS

RON, ROM, and the surgical follow-up rate increased steadily from the benign through intermediate to malignant categories. The omission of NIFTP from malignant lesions reduced the calculated ROM in indeterminate categories and improved the stratification between AUS and SFN. ROM in AUS was distinct from SFN. AUS has a well-balanced sensitivity and specificity favouring a screening rather than a diagnostic category. The calculated RON/ROM was significantly higher in AUS (1.56), compared to SFN (1.03) and SM (1.05), in agreement with current BSRTC management recommendations.

CONCLUSIONS

AUS is an important screening category and should remain with the addition of subcategorisation. RON and surgical follow-up rates are essential quality indicators. The RON/ROM ratio could be utilised to determine appropriate management for each diagnostic category on an institutional basis.

Outcomes of the Bethesda system for reporting thyroid cytopathology: Real-life experience

OBJECTIVE

The 2017 revised Bethesda System for Reporting Thyroid Cytopathology (BSRTC) included new malignancy rates for each category as well as new management recommendations. Here, we evaluate the malignancy rate and test performance for BSRTC categories in a middle-sized institution outside the United States (US).

DESIGN

Retrospective single centre case series with chart review.

PATIENTS

All patients who underwent thyroid surgery with a preoperative BSRTC between the years 2010 and 2018 at our institution.

MEASUREMENTS

In order to assess the malignancy rate for each BSRTC, all medical records were reviewed to collect demographics, nodule's size, BSRTC and final pathology.

RESULTS

Three hundred and sixty-four patients were included, with an overall malignancy rate of 34.3%. The malignancy rate for BSRTC categories I-VI was as follows: 13.3%, 5.1%, 25.0%, 24.4%, 91.3% and 95.2%, respectively. The most sensitive test was when BSRTC III-VI were evaluated (91%). Overall best performance (sensitivity, specificity, PPV, NPV and accuracy) was obtained when BSRTC V-VI were grouped together with a substantial decrease when adding BSRTC III-IV (90%, 97%, 94%, 95%, 95% vs, respectively, 91%, 73%, 62%, 95%, 79%, respectively).

CONCLUSIONS

Despite differences from the reported 2017 BSRTC malignancy rates, we demonstrated that the revised 2017 BSRTC management recommendations for thyroid nodules are also valid in smaller non-US centre, supporting its use globally.

Artificial Intelligence in Thyroid Fine Needle Aspiration Biopsies

BACKGROUND

From cell phones to aerospace, artificial intelligence (AI) has wide-reaching influence in the modern age. In this review, we discuss the application of AI solutions to an equally ubiquitous problem in cytopathology - thyroid fine needle aspiration biopsy (FNAB). Thyroid nodules are common in the general population, and FNAB is the sampling modality of choice. The resulting prevalence in the practicing pathologist's daily workload makes thyroid FNAB an appealing target for the application of AI solutions.

SUMMARY

This review summarizes all available literature on the application of AI to thyroid cytopathology. We follow the evolution from morphometric analysis to convolutional neural networks. We explore the application of AI technology to different questions in thyroid cytopathology, including distinguishing papillary carcinoma from benign, distinguishing follicular adenoma from carcinoma and identifying non-invasive follicular thyroid neoplasm with papillary-like nuclear features by key words and phrases. Key Messages: The current literature shows promise towards the application of AI technology to thyroid fine needle aspiration biopsy. Much work is needed to define how this powerful technology will be of best use to the future of cytopathology practice.

The impact of repeat fine-needle aspiration in thyroid nodules categorized as atypia of undetermined significance or follicular lesion of undetermined significance: A single center experience

BACKGROUND

Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) is the most controversial category of the Bethesda System. The present study was conducted to compare the histological findings in a series of thyroid nodules diagnosed with AUS/FLUS after single or repeat fine needle aspiration (FNA) cytology.

METHODS

Retrospective analysis of our institution's series of 514 patients with an initial diagnosis of AUS/FLUS between 11/2011 and 02/2020.

RESULTS

Of 4887 FNA samples, 11.8% were classified as AUS/FLUS. Of patients with an initial AUS/FLUS diagnosis, 11.5% (59/514) underwent surgery after a single FNA, 55.4% (285/514) had a repeat FNA, and 32.7% (168/514) were either observed or lost to follow-up. Surgical pathology was available in 123 cases (23.9%), and malignancy was confirmed in 32.5% (40/123) cases, with similar rates in the single 32.2% (19/59) and repeat FNA 32.8% (21/64) groups. Repeat FNA reclassified 78.9% of the AUS/FLUS cases to a different category: 57.2% were reclassified as benign, 10.5% as follicular neoplasm, and 5.6% as suspicious for malignancy or malignant. The rates of nonneoplastic benign lesions were 52.5% (31/59) and 31.2% (20/64) in the single and repeat FNA groups, respectively (P = .018). The rates of follicular adenomas were higher when repeat FNA was performed (23/64, 35.9%) compared with a single FNA (9/59; 15.2%) (P = .013).

CONCLUSION

In this series, a repeat FNA in cases of AUS/FLUS increased detection of follicular adenomas but not the detection of malignancy. Repeat FNA reduced the rate of benign nonneoplastic lesions by 40% in the surgical samples.

Thyroid cytology in Pakistan: An institutional audit of the atypia of undetermined significance/follicular lesion of undetermined significance category

INTRODUCTION

Fine needle aspiration cytology (FNAC), along with thyroid ultrasound, is an important tool in evaluation of thyroid nodules that helps in further management of these patients in making a decision of surgical intervention vs follow-up. The Bethesda System for Reporting Thyroid Cytopathology category III of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) has risk of malignancy (ROM) ranging from 5% to 15%. The aim of the present study was to describe the frequency of AUS/FLUS in thyroid gland FNACs and the surgical outcomes of these cases.

METHODS

The integrated laboratory management system retrieved the thyroid FNACs from 2010 to 2018 and subsequent surgical pathology specimens. For the AUS/FLUS cases, data regarding patient demographics, cytology and histological diagnoses were recorded. The results were tabulated as the overall frequency of AUS/FLUS in thyroid FNACs, cytohistological correlation (benign and malignant) and ROM.

RESULTS

Over a period of 9 years, 256 (10.9%) cases out of 2342 thyroid FNACs were reported as AUS/FLUS at our institution. Mean age was 43.5 years. The majority (70.3%) of patients were female. Seventy-two of 104 resection specimens (69.2%) were reported as benign and 32 cases (30.7%) had malignant diagnosis. Upper-bound ROM was 30.7% (32 cases with malignant diagnosis out of 104 resection specimens). Lower-bound ROM was calculated as 12.5% (32 cases with malignant diagnosis out of 256 total AUS diagnosis).

CONCLUSION

The AUS/FLUS category of thyroid cytology and associated ROM remain an evolving area. Individual institutions should monitor the frequency and include ROM in the dashboard indicators to remain within the recommended range.

Usability of EU-TIRADS in the Diagnostics of Hürthle Cell Thyroid Nodules with Equivocal Cytology

The aim of this study was to compare the diagnostic effectiveness of EU-TIRADS in two groups of nodules with equivocal cytology (categories III-V of Bethesda system), with and without Hürthle cells (HC and non-HC). The study included 162 HC and 378 non-HC nodules with determined histopathological diagnosis (17.9% and 15.6% cancers). In both groups calculated and expected risk of malignancy (RoM) for high, intermediate and benign risk categories of EU-TIRADS were concordant. RoM for low risk category was higher than expected in both groups, but especially in HC (HC: 13.9%, non-HC: 7.0%, expected: 2-4%). The majority of cancers in HC of that category were follicular thyroid carcinomas (FTC) and Hürthle cell thyroid carcinoma (HTC) (60.0% vs. non-HC: 16.7%). The diagnostic efficacy of EU-TIRADS was lower in HC (the area under the receiver operating characteristics curve (AUC): 0.621, sensitivity (SEN): 44.8%, specificity (SPC): 78.9% for high risk threshold) than in non-HC (AUC: 0.711, SEN: 61.0%, SPC: 77.7%). AUC was the highest for category V (AUC > 0.8, both groups) and the lowest for category IV (inefficient, both group). If intermediate risk category was interpreted as an indication for surgery, 25% of cancers from category III and 21.4% from category IV would not be treated in the HC group (0.0% and 7.4% from non-HC group, respectively). EU-TIRADS does not aid making clinical decisions in patients with cytologically equivocal HC nodules, particularly those classified into category IV of Bethesda System for Reporting Thyroid Cytopathology (BSRTC).

Indian experience of AUS/FLUS diagnosis: is it different from rest of Asia and the West?-A systematic review and meta-analysis

Background

Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is the most heterogeneous subcategory of the Bethesda system for thyroid cytopathology with laid down permissible limits of frequency and risk of malignancy (ROM). Due to differences in thyroid clinical practice worldwide, variations have been found in frequency, resection rates (RR) and ROM. Therefore, this systematic review and meta-analysis of AUS/FLUS across different regions was conducted and comparison of data from India was done with the rest of Asia and the West.

Methods

We searched PubMed and Google search engines from January 2009-Dec 2019 using terms "AUS Thyroid" and "FLUS Thyroid". Meta-analysis was performed using DerSimonian-Laird method and 95% confidence intervals were calculated using random effects model. Independent samples t-test was used to compare frequency, RR, and ROM of AUS/FLUS between India, rest of Asia and the West.

Results

Out of 15,000 studies on internet, 60 (18 Indian, 12 Asian and 30 Western) were included. Total aspirates were 201,657; 14,279 Indian, 62,448 Asian, 124,930 Western. Pooled estimates were: frequency 7.3% (6.3-8.3%), RR 41.9% (37.4-46.6%), ROM 33.3% (26.8-39.9%). Pooled prevalence of rate did not vary significantly across the three regions. Pooled prevalence of RR was highest in India (52.9%) and lowest in rest of Asia (26.5%); of ROM was highest in Asia (45.9%), lowest in the West (26.3%) (P<0.01). Statistical analysis demonstrated publication bias, limited to Indian and Western studies. Papillary thyroid carcinoma was the most common surgical diagnosis (87.9%; 1,082/1,231).

Conclusions

This meta-analysis showed differences in thyroid clinical practice followed in India, rest of Asia and the West. Although pooled prevalence of rate of AUS/FLUS was similar across the three, pooled RR and ROM varied. AUS/FLUS nodules were more frequently resected in Indian and Western studies than in rest of Asia. ROM was higher than recommended values in all three areas, being intermediate for India.

Indeterminate thyroid nodules. The role of 18F-FDG PET/CT in the "era" of ultrasonography risk stratification systems and new thyroid cytology classifications

PURPOSE

To evaluate the reliability of ¹⁸F-FDG PET/CT in distinguishing differentiated thyroid cancers (DTCs) and follicular neoplasms (FNs) from nodular hyperplasias (NH) in thyroid nodules with indeterminate cytology according to the Italian consensus for the classification and reporting of thyroid cytology (ICCRTC). We also tested whether the ¹⁸F-FDG PET/CT result was an independent risk factor for DTCs or FNs when sex, age, nodule dimensions, the European Thyroid Imaging and Reporting Data System (EU-TIRADS) and ICCRTC were considered.

METHODS

We evaluated all patients with thyroid nodules and indeterminate cytology from September 2015 to May 2019; nodules were classified as low risk (TIR3A) and high risk (TIR3B) according to the ICCRTC. Neck ultrasonography features according to EU-TIRADS were re-evaluated and ¹⁸F-FDG PET/CT performed. All these patients were surgically treated.

RESULTS

We included 111 patients; 67 nodules were classified as TIR3A and 44 as TIR3B. Overall, we found 27 DTCs, 57 NHs and 27 FNs. Among 73 FDG-negative nodules, we found four low-risk papillary thyroid cancers. All follicular thyroid cancers were identified by ¹⁸F-FDG-PET/CT. All TIR3A with low-risk US and negative ¹⁸F-FDG-PET/CT were NH. In TIR3A nodules, the sensitivity, specificity, negative and positive predictive values (NPV, PPV) of ¹⁸F-FDG PET/CT and EU-TIRADS for DTCs were 77.8%, 41.4%, 92.3%, 17.1% and 66.7%, 56.9%, 91.7%, 19.4%, respectively. In TIR3B nodules, the sensitivity, specificity, NPV and PPV of ¹⁸F-FDG PET/CT and EU-TIRADS for DTCs were 88.9%, 38.5%, 83.3%, 50% and 88.2%, 58.3%, 87.5%, 60%, respectively. On multivariate analysis, ¹⁸F-FDG-PET/CT (OR 9.04), ICCRTC (O.R. 7.57) and EU-TIRADS (OR 4.41) were all independent risk factors associated to DTCs and FNs.

CONCLUSION

¹⁸F-FDG-PET/CT is a reliable rule-out test for DTC even in thyroid nodules with indeterminate high-risk results. In this subgroup, PPV also tends to be considerable. ¹⁸F-FDG-PET/CT results, ICCRTC and EU-TIRADS proved independent risk factors associated to DTCs and FNs.

Exploring the Inter-observer Agreement Among the Members of the Italian Consensus for the Classification and Reporting of Thyroid Cytology

Classification schemes for reporting thyroid cytology of fine needle aspiration (FNA) of thyroid nodules are largely used in clinical practice, but the level of inter-observer agreement among cytopathologists is poorly acknowledged. The present study aimed to explore the inter-observer agreement among the experienced authors of the 2014 Italian Consensus for Classification and Reporting of Thyroid Cytology (ICCRTC). A stratified randomization was performed in order to obtain a sample homogeneously distributed and representative of all ICCRTC classes. Four high-experience raters were randomly selected among the extensors of the Italian consensus. They independently reviewed 60 FNA samples blindly of the initial cytological report and clinical features. Their overall agreement was evaluated according to Fleiss' kappa. The overall inter-observer agreement was moderate (κ 0.46). Specifically, a good agreement was found when the samples were consistent for malignancy (TIR5) or were not adequate for diagnosis (TIR1) (κ 0.67 and κ 0.73, respectively). A moderate agreement was present for suspicious-for-malignant category (TIR4), and a fair agreement was recorded in the two intermediate ones (TIR3A and TIR3B) (κ 0.36 and κ 0.35, respectively). For clinical purposes, the agreement was good (κ 0.74) in differentiating cases with surgical indication (TIR4/TIR5) from those in which surgery is not essential or requires limited extension (TIR3B/TIR3A/TIR2). In conclusion, the present study confirms the reliability of ICCRTC. These data represent a reference for cytopathologists using this system and are useful for the practice of clinicians and surgeons.

High risk of malignancy in cases with atypia of undetermined significance on fine needle aspiration of thyroid nodules even after exclusion of NIFTP

BACKGROUND

Fine needle aspiration cytopathology (FNAC) is the most reliable tool for evaluating thyroid nodules. However, diagnosing Bethesda category III, atypia/follicular lesion of undetermined significance (AUS/FLUS), is a major limitation. The aim of this study was to evaluate the risk of malignancy (RoM) in AUS/FLUS nodules. A systematic review was also carried out analyzing the largest series.

METHODS

Totally 1750 cases (9%) diagnosed with AUS/FLUS were evaluated retrospectively out of 19 392 cases within last 13 years. All patients undergoing surgery for AUS/FLUS were included into the study. Histopathology results were correlated; the impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) diagnosis on RoM is evaluated.

RESULTS

Of the 280 patients (16%) undergoing surgery, neoplasia were detected in 177 (RoN:63.2%) and malignancy in 119 (RoM:42.5%) of these neoplasia. Follicular variant of papillary thyroid carcinoma (FVPTC) was the commonest malignancy (55.5%). Additional 58 (20.7%) nodules were neoplastic, of which 26 (9.3%) were encapsulated follicular tumors with unknown malignancy potential (FT-UMP) and 32 (11.4%) were follicular adenomas. The remaining 103 patients (36.8%) had non-neoplastic nodules. After reevaluation of the encapsulated FVPTC cases, 20 of them were NIFTP and RoM dropped to 35.4% with a relative decrease of 16.7% and an absolute decrease of 7.1%.

CONCLUSION

In our series, 42.5% of nodules with AUS/FLUS were malignant; 63.2% of them were neoplastic. The RoM and RoN for AUS/FLUS nodules are still much higher than the revised expected RoM of international guidelines even after NIFTP cases excluded. Therefore, current recommendations should be reevaluated periodically in view of detailed clinicopathologic studies.

The importance of risk of neoplasm as an outcome in cytologic-histologic correlation studies on thyroid fine needle aspiration

BACKGROUND

The introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) altered the practice of thyroid pathology and reduced the risk of malignancy (ROM) associated with the indeterminate categories in the Bethesda system for reporting thyroid cytopathology (TBSRTC). It has been proposed that the evaluation of the risk of neoplasm (RON) is important in cytologic-histologic correlation studies.

METHODS

A total of 5224 thyroid aspirates were performed at our institution during an 8-year period. Of the 1475 cases (28%) with surgical follow-up, the histologic diagnoses comprised benign non-neoplastic (BNN, n = 669), follicular adenoma (FA, n = 188), NIFTP (n = 42), papillary microcarcinoma (PMC) (n = 223), and malignant neoplasm excluding PMC (n = 353). The RON was calculated to include neoplasia with low risk biologic behavior (FA, NIFTP, PMC) and malignant neoplasms. In contrast, the ROM was reserved for malignant neoplasms excluding PMC.

RESULTS

The RON for each TBSRTC category was: nondiagnostic (ND) 38.3%, benign 20.9%, atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) 63.2%, follicular neoplasm or suspicious for follicular neoplasm (FN/SFN) 83.9%, suspicious for malignancy (SFM) 94%, and malignant 100%. The ROM excluding PMC was: ND 14%, benign 1.6%, AUS/FLUS 17.8%, FN/SFN 28.4%, SFM 84.4%, and malignant 99.5%.

CONCLUSIONS

The RON and ROM support the recommended management guidelines from TBSRTC for all categories, except for FN/SFN. Histopathologic follow-up of FN/SFN aspirates in our study contain a very high rate of neoplasm (83.9%), which might support the management preference of conservative surgery.

Pitfalls in Thyroid Cytopathology

Fine-needle aspiration (FNA) is among the first diagnostic tools used in the evaluation of thyroid nodules. It has the ability to triage patients with benign and malignant lesions, thus defining the optimum clinical and/or surgical management. The Bethesda System for Reporting Thyroid Cytopathology has found worldwide acceptance. Thyroid FNA offers high positive predictive value (97%-99%), with sensitivities and specificities of 65% to 99% and 72% to 100%, respectively. Nonetheless, many potential diagnostic pitfalls exist that can lead to false-positive and/or false-negative results. This article discusses several of the potential pitfalls in the cytologic evaluation of thyroid lesions.

Measures to reduce diagnostic error and improve clinical decision making in thyroid FNA aspiration cytology: A proposed framework

Thyroid fine-needle aspiration cytology (FNA) and histopathology can be subjective areas of medical diagnosis and subject to different interpretations. On the basis of the authors' personal experience, 12 recommendations with potential to improve clinical decision making, ensure quality, and reduce diagnostic error in thyroid FNAC and histopathology are presented. 1) use a standardized reporting terminology for thyroid FNAC; 2) understand and explain to service users the limitations of cytology and the standardized thyroid FNAC reporting terminology used; 3) the cytopathologist should review all relevant clinical and ultrasound findings, if feasible; 4) include the risk of malignancy in all FNAC reports if feasible; 5) collect data to calculate the local institutional risk of malignancy for FNAC if feasible; 6) accept that nondiagnostic FNAC will include small numbers of carcinomas; 7) use rapid on-site evaluation and/or educational sessions for aspirators if the nondiagnostic aspiration rate is high; 8) know the diagnostic pitfalls of both cytology and histopathology; 9) use special immunohistochemical and molecular techniques that are evidence-based; 10) make use of second opinions, either in-house or interinstitutional; 11) multidisciplinary discussion of cases before surgery or therapy is invaluable; and, finally, 12) manage patient and clinician expectations of thyroid cytology and histopathology. These 12 recommendations may assist in quality-improvement initiatives and may reduce diagnostic errors in thyroid cytology and histopathology. Thyroid multidisciplinary case discussion remains the principal, overarching method for error reduction and for providing high-quality clinical decision making.

Differences in cytopathologist thyroid nodule malignancy rate

OBJECTIVES

The accuracy of a cytological diagnosis obtained by fine needle aspiration is influenced by several factors including the technique used and the experience of both the aspirator as well as the cytologist. In this project we planned to evaluate the interobserver differences of thyroid nodule cytopathology in our medical centre.

METHODS

The study was conducted using retrospective pathology reports from a single academic centre from August 2013 to September 2017. We compared the sensitivity, specificity, negative and positive predictive values, malignancy rates, and accuracy of two cytopathologists who evaluated thyroid nodules.

RESULTS

We included 287 fine needle aspirations of thyroid nodules in the study. Approximately one fifth (18.5%) of patients had surgery and the rate of malignancy was 40%. There was a similar frequency of use of all thyroid Bethesda system (TBS) categories with the exception of TBS 3 (8.0% and 21.2%, P = .01). As a consequence, the malignancy rate was different in TBS 3 category (40% vs 17%, P = .545).

CONCLUSIONS

There are interobserver differences in the evaluation of thyroid nodules. Clinicians should be aware of such differences because they affect the malignancy rate in each TBS category.

Molecular-derived estimation of risk of malignancy for indeterminate thyroid cytology diagnoses

INTRODUCTION

One of the key features of the Bethesda System for Reporting Thyroid Cytopathology is the risk of malignancy (ROM), which guides management for each diagnostic category. However, calculation of the ROM can be challenging for indeterminate diagnoses because only a portion of cases will be resected for cytologic-histologic correlation (CHC) analyses. In the present study, we used the probability of cancer information from ThyroSeq, version 3, reports to calculate the molecular-derived (MD) ROM for indeterminate categories.

MATERIALS AND METHODS

Cytology cases with indeterminate BSRTC diagnoses and adequate molecular test results were retrieved from our cytopathology laboratory for a 12-month period. The probability of cancer information from the ThyroSeq, version 3, molecular reports were tabulated, and the mean ROM was calculated for each diagnostic category. The MDROM included noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) as a "malignant" outcome because it is considered a surgical disease.

RESULTS

A total of 361 cases had adequate material for molecular testing. The diagnostic distribution was as follows: atypia of undetermined significance/follicular lesion of undetermined significance, 271 cases (75.1%), follicular neoplasm/suspicious for a follicular neoplasm, 59 cases (16.3%), and Hürthle cell type/suspicious for a follicular neoplasm, Hürthle cell type, 31 cases (8.6%). The corresponding estimated MDROMs were 14.9%, 32.6%, and 34.4%. A comparison with the CHC data was performed, and the 95% confidence intervals of the MDROMs overlapped well with the 2 endpoint CHC values.

CONCLUSIONS

Calculation of the MDROMs provides a new method to approximate the ROMs of indeterminate diagnoses and has the advantage of potentially evaluating all cases, not just those resected. Furthermore, for those using the same platform, interinstitutional comparisons will be possible.

Differential outcomes of patients with thyroid FNA diagnoses of AUS/FLUS with and without nuclear atypia: The potential need for separation in the Bethesda System

BACKGROUND

In the current version of The Bethesda System (TBS) for thyroid cytopathology, the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category has an estimated risk of malignancy of 10% to 30%. Diagnostic criteria include presence of nuclear atypia, suggestive of papillary thyroid carcinoma (PTC), as well as other types of atypia, which can be seen with non-malignant entities. Aim of this study was to investigate differential outcomes of AUS/FLUS, based on specific morphologic criteria, and assess their respective malignancy risks.

METHODS

From a total of 1233 patients undergoing thyroid FNAs between 2010 and 2014 at the University of Washington, 119 had AUS/FLUS without nuclear atypia, and 64 with nuclear atypia. Outcomes for patients with and without nuclear atypia (with the exception of 24 patients lost to follow-up) were evaluated and results were compared.

RESULTS

16/57 (28.1%) patients with AUS/FLUS and nuclear atypia subsequently had carcinomas on thyroidectomy, statistically higher than the 8/102 patients (7.8%, P = .001) without nuclear atypia. When comparing only patients who underwent surgery (n = 63), again those with AUS/FLUS and nuclear atypia had statistically higher rates of carcinoma (16/31, 51.6%), compared to those without (8/32, 25%; P = .0394). Overall, 24/159 (15.1%) of patients with AUS/FLUS had carcinoma on subsequent histology.

CONCLUSION

Malignancy rates for AUS/FLUS were in line with TBS estimated risks. However, our data demonstrate that the presence or absence of nuclear atypia is associated with different malignancy rates, suggesting the possibility that the AUS/FLUS category may best be split into two subcategories with different implied risks of malignancy.

Malignancy Rate in Thyroid Nodules with Atypia or Follicular Lesion of Undetermined Significance

Introduction  Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) is one of the six diagnostic categories of the Bethesda System for Reporting Thyroid Cytopathology. The prevalence of malignancy among Bethesda category III cytology is variable, ranging from 5% to 37% in the literature. Objective  To determine the rate of malignancy in thyroid nodules reported as Bethesda category III. Methods  A total of 495 patients underwent surgical intervention for thyroid nodules from January 2015 to December 2017. The present study included 81 cases reported as Bethesda category III, and their medical records were reviewed. Results  Out of 495 fine-needle aspiration cytology samples, 81 (16.4%) samples were labeled as AUS/FLUS. Among these 81 patients, the mean age was 43.0 years (± 13.9), with only 11 (14%) patients older than 55 years of age. Most of our patients were female ( n  = 69; 85.2%), and the rest were male. The rate of malignancy based on the final histology was of 33.3% ( n  = 27). The majority were 17 cases (21%) of papillary carcinoma, followed by follicular carcinoma ( n  = 6) (7.4%). Conclusion  The risk of malignancy can be higher than it is commonly believed, and guidelines should be based on the data from the institutions themselves for a better assessment of the outcomes.

Testing for Afirma in Thyroid Nodules with High-Risk Indeterminate Cytology (TIR3B): First Italian Experience

A percentage of 15 to 30% of thyroid fine-needle aspiration (FNA) is indeterminate, i.e., TIR3A and TIR3B according to the Italian consensus for thyroid cytology. Afirma, a molecular analysis of thyroid FNA specimens, has recently gained popularity as an adjunct to microscopic cytological evaluation, in order to avoid diagnostic surgery in patients with indeterminate thyroid cytology. We described the first Italian experience with Afirma tests in a single Italian institution and assessed the performance of the Afirma test in TIR3B. Moreover, this is a preliminary study to assess the patient response to the offer of Afirma testing. The Afirma test was proposed to 67 patients with thyroid nodules that had yielded TIR3B cytology. Fifty-one patients (76.1%) chose the Afirma test, 25/51 underwent the test but the remaining 26 did not because of cost. A total of 41/67 (61.2%) patients underwent surgery, and 22/41 (53.7%) nodules were carcinomas. Of the 25 tested by Afirma, 9 (36%) were classified as Afirma-suspicious (Afirma-S); seven of them underwent surgery, and in 6/7 (85.7%), a cancer was proven at histology. Afirma is the procedure that many Italian patients with TIR3B lesions would choose. However, its routine clinical application in Italy is currently limited by high costs for the patient. When Afirma is performed in this setting of patients, the cancer risk of suspicious result is higher than that expected in all the series of TIR3B. Therefore, testing for Afirma in these nodules may be useful for managing patients and tailoring their surgical approach.

Rapid On-site Molecular Evaluation in thyroid cytopathology: A same-day cytological and molecular diagnosis

BACKGROUND

Thyroid fine-needle aspirates (FNAs) with undetermined morphology can be outsourced to centralized laboratories for comprehensive molecular profiling. When a local, rapid screening rules out easily detectable BRAF and NRAS mutations outsourcing is minimized, leading to cost savings. The fully automated Idylla technology, that does not require trained staff, is an emerging option. However, Idylla platform has only been validated to process formalin fixed paraffin embedded (FFPE) sections. Here we investigate whether also the FNA needle rinse could be genotyped by the same cytopathologist who performs the FNA, a procedure that can be termed rapid on site molecular evaluation (ROME).

METHODS

To validate this approach, the Idylla BRAF and NRAS Test was performed on the rinses from 25 simulated (bench-top) FNAs, in a first part of the study. Genotyping data were compared with those obtained on matched histological FFPE blocks. The second part of the study was carried out on 25 prospectively collected routine FNAs to assess the performance of the Idylla BRAF and NRAS assay against a gold standard real time polymerase chain reaction method.

RESULTS

Idylla NRAS-BRAF Mutation Test was performed on needle rinse as well as histological FFPE blocks. A sensitivity of 88.9%, a specificity of 100.0% were obtained comparing the Idylla NRAS-BRAF Mutation Test on needle rinse to the reference method.

CONCLUSIONS

The FNA needle rinse can be directly genotyped. This obviates the need of cell block preparation, making possible a rapid combined morphological and molecular evaluation. Since DNA extraction is no longer necessary, the cytopathologist can perform ROME him/herself.

Impact of the Italian Society of Anatomic Pathology and Diagnostic Cytology Classification of Thyroid Nodules in the Treatment of Indeterminate Follicular Lesions: Five-Year Results at a Single Center

PURPOSE

Aim of the study was to assess the impact of the Italian Society of Anatomic Pathology and Diagnostic Cytology (SIAPEC) classification of 2014, on the treatment of indeterminate thyroid lesions (TIR3).

METHODS

We retrospectively analyzed patients undergoing thyroid surgery for TIR3 lesions between 2013 and 2018, at the General Surgery Department of Trieste University Hospital. According to the SIAPEC classification, patients were divided into TIR3A and TIR3B groups. All patients treated before 2014 underwent surgical treatment, and surgical specimens were retrospectively classified after revision of fine-needle aspiration cytology. Starting 2014, TIR3A patients were treated only when symptomatic (i.e., coexistent bilateral thyroid goiter or growing TIR3A nodules), whereas TIR3B patients always received surgical treatment. Hemithyroidectomy (HT) was the procedure of choice. Total thyroidectomy (TT) was performed in case of concurrent bilateral goiter, autoimmune thyroid disease, and/or presence of BRAF and/or RAS mutation. Lastly, we analyzed the malignancy rate in the two groups.

RESULTS

29 TIR3A and 90 TIR3B patients were included in the study. HT was performed in 10 TIR3A patients and 37 TIR3B patients, respectively, with need for reoperation in 4 TIR3B (10.8%) patients due to histological findings of follicular thyroid carcinoma >1  cm. The malignancy rates were 17.2% in TIR3A and 31.1% in TIR3B, (p = 0.16). Predictability of malignancy was almost 89% in BRAF mutation and just 47% in RAS mutation.

CONCLUSIONS

The new SIAPEC classification in association with biomolecular markers has improved diagnostic accuracy, patient selection, and clinical management of TIR3 lesions.

Prognosis of patients with differentiated thyroid carcinomas having a preoperative cytological report of indeterminate at low or high risk. A multicenter study

BACKGROUND

Italian cytology system for thyroid fine-needle aspiration (FNA) includes indeterminate lesions at low- (Tir 3A) and high-risk (Tir 3B). The present retrospective multicenter study was undertaken to compare the histological type of cancers and disease-free survival in these two groups.

METHODS

Eight institutions participated. Thyroid cancer patients diagnosed and followed-up after Tir 3A or Tir 3B were reviewed. Histological diagnosis was adopted as the gold standard. Patients were defined with cancer recurrence or no evidence of disease. Disease-free survival (DFS) was calculated. A non-parametric statistical analysis was used. DFS was estimated by Kaplan-Meier method and Hazard Ratio (HR) defined the slope of curves.

RESULTS

Two hundred and nine patients (median DFS 24 months) were enrolled and a 6.3% of these recurred. Tir 3B group had higher age (p = 0.014), larger cancer size (p = 0.0002), shorter DFS (p = 0.003), higher number of aggressive cancers (p = 0.006), and relapse frequency double than Tir 3A. At survival curves analysis, Tir 3B group had HR of 2.37 with respect to Tir 3A. At Cox's proportional hazard regression analysis histology was the only significant predictor of relapse.

CONCLUSIONS

While patients with thyroid FNA of Tir 3B should be addressed to surgery due to high likelihood of more aggressive cancer, a diagnostic surgery could be avoided in patients with Tir 3A if concurrent unsuspicious clinical features are found.

Preoperative Diagnostic Categories of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features in Thyroid Core Needle Biopsy and Its Impact on Risk of Malignancy

This study was designed to evaluate the preoperative diagnostic categories of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) using thyroid core needle biopsy (CNB) and to analyze its impact on the risk of malignancy (ROM). A total of 2687 consecutive thyroid CNBs were reviewed retrospectively and classified into six diagnostic categories using a standardized reporting system similar to the Bethesda System for Reporting Thyroid Cytopathology. Diagnostic categories of CNBs were compared with the final surgical diagnoses, and the ROM in each category was calculated both before and after excluding NIFTP from malignancy. Of 946 surgically resected cases, 683 were diagnosed as papillary thyroid carcinoma (PTC), and 32 (4.7% of PTC) were reclassified as NIFTP. The CNB diagnostic categories of NIFTP were as follows: follicular neoplasm in 20 (62.5%; 14, with nuclear atypia), indeterminate lesion in 11 (34.4%), and suspicious for malignancy in one (3.1%). When combined, NIFTP and encapsulated follicular variant of PTC (EFVPTC) were more often categorized as follicular neoplasm compared with other PTC variants including infiltrative FVPTC. Exclusion of NIFTP from malignant diagnosis led to a significant decrease in the ROM in follicular neoplasm with nuclear atypia category. Thus, thyroid CNB enables to differentiate NIFTP/EFVPTC from other PTCs, providing a useful guide for optimal treatment in patients with these tumors.